The present invention relates to a defrost control method for a refrigerator, and particularly to a defrost control method which evaluates the defrost time, the temperature inside the refrigerator and the position of the doors and then initiates the defrost operation when the three conditions are satisfied.
A prior art defrost control method, as shown in FIG. 1, is a method which initiates the defrost operation if the operation period of the compressor reaches a predetermined time, irrespective of the temperature inside the refrigerator. A typical example of the method is disclosed in U.S. Pat. No. 4,528,821. However, the problem with this method is that the defrost operation is executed while the operation of the compressor is switched from the "on" state to the "off" state or during a period when the temperature within the refrigerator is at the upper end of its range at which stored foods deteriorate.
Accordingly, in order to avoid this problem, as shown in FIG. 2, the defrost operation is executed after the temperature in the refrigerator is reduced by causing the compressor to operate prior to the defrost operation or when, as disclosed in Japanese Utility Laid-Open Publication No. 64-22972, the temperature in the refrigerator and the defrost time are evaluated and the two conditions are satisfied. However, the problem with this method is that during the operation in low temperature, a refrigerator wastes power by causing the compressor to operate prior to the defrost operation and then the temperature in the refrigerator falls excessively which causes the stored foods to become frozen.
Another defrost control method is a method which evaluates the position of the doors. A typical example is disclosed in U.S. Pat. No. 4,297,852. Because this does not simultaneously evaluate the temperature, the defrost time and the position of the doors, this method also has the above problem.